SINCE Donald Trump won America’s presidential election investors have salivated over the prospect of lower taxes. Mr Trump has promised to cut corporation tax, a levy on firms’ profits, from 35% to 15%. Republicans remain in charge of both houses of Congress; Paul Ryan, the speaker of the House of Representatives, wants to cut the levy to 20%. The coming reforms, though, are about more than just lower rates. Republicans want to overhaul business taxes completely. Unfortunately, this task is far from straightforward.

America’s corporate-tax rate, which reaches 39.6% once state and local levies are included, is the highest in the rich world. But a panoply of deductions and credits keeps firms’ bills down. These include huge distortions, such as a deduction for debt-interest payments, as well as smaller scratchings of pork like special treatment for NASCAR racetracks. After all the deductions are doled out, corporate-tax revenues are roughly in line with the average in the rest of the G7, according to economists at Goldman Sachs.

Still, a high tax rate and a narrow tax base is a glaringly inefficient combination. Politicians of all…Continue reading